In a color video camera, the image of an object is detected by three imaging devices, such as CCD image sensors, each sensitive to a particular light component. Typically, an array of three CCD image sensors will produce analog image signals comprising red (R), green (G), and blue (B) signals. An analog-to-digital (A/D) converter converts each of the R, G, and B signals into corresponding digital signals. The digital R, G, and B signals are pre-processed by a pre-processing circuit to correct errors in the image signals such as pixel errors and shading irregularities.
Following pre-processing, the corrected signals are subject to further processing such as linear matrix processing, gamma correction, knee correction, and/or aperture compensation by a separate processing circuit. The processed signals are converted into brightness data and color-difference data. The digital brightness data and color-difference data are converted by a digital-to-analog (D/A) converter into corresponding analog signals. An encoder codes the analog brightness signal and analog color-difference signals to produce a composite image signal for display.
The digital brightness data and color-difference data may also be supplied to a data rate converter. The data rate converter modifies the clock rate of the received data to another clock rate. For example, the received data may be converted to data having a rate compatible with the recording operation of a video tape recording apparatus.
Each of the pre-processing circuit, the processing circuit, and the data rate converter operate in accordance with respective sets of predetermined parameter data. Typically, such parameter data is pre-stored into each of the pre-processing circuit, the processing circuit, and the data rate converter.
Upon a loss of power to the video camera or to one of its components, parameter data stored in a pre-processing circuit, a processing circuit, a data rate converter, or elsewhere, can be lost or damaged. Also, parameter data can be lost or damaged by power line noise or by electrostatic discharges. Loss of or damage to the stored parameter data usually results in erroneous operation of the video camera and in severe interruptions in signal processing operations.
To minimize improper camera operation, stored parameter data may be checked to detect loss or damage by reading out the stored parameter data. For example, the parameter data stored in each circuit utilizing such parameter data may be read to verify the parameter data. Such a verification process requires significant software overhead and is burdensome. The verification process is also inefficient since parameter data is infrequently lost or damaged.